326 EXPLANATIONS OF TERMS. 



Peristaltic. The intestines of animals are constantly undergoing a sort of motion, 



by which their contents are moved through them, which appears like that of 



the creeping of a worm. It is called their vermicular or peristaltic motion. 

 Permanently elastic, applied to fluids, denotes those which retain their elastic state 



at the ordinary pressure and temperature of the atmosphere. 

 Petals, the colored leaves of the flowers of plants. 

 Pituitary, one of the names of the membrane lining the nose. 

 Quadruman&us, four-handed, belonging to the order Qv.adru.mana 

 Radiation of heat, the passing of heat from bodies through an intervening space in 



rays like light, used in contradistinction to the direct transmission of heat by 



contact. 



Radiated, arranged like the radii or rays of a circle. 

 Rationale, a detail of any course of phenomena or operations with the principle or 



reason on which they proceed. 

 Retina, a nervous membrane situated on the back part of the eye, and intended 



to receive the images of external objects ; formed by the expansion of the optic 



nerve as it comes out from the brain into the eye. 

 Retrograde, going backward, moving backward. 

 Reviviscence, renewal of life. 

 Rugosity, roughness, inequality of any kind. 

 Ruminate, to chew the cud : this operation is described, pp. 45, 46. 

 Saliva, spittle, the liquid which moistens the mouth, and mixes with the food in 



mastication. 

 Sapid, having taste. 

 Schneiderian, one of the names of the membrane lining the nose, derived from the 



name of the anatomist who first described it. 

 Sea-anemone, an animal of the class of Zoophytes, so called from some degree of 



resemblance in its form to an expanded flower. 

 Serrated, notched like a saw. 

 Spinal, belonging to the back-bone or spine. 

 Spleen, a small oblong organ situated on the left side of the stomach, just under the 



ribs ; of a reddish blue or purple color, and very full of blood. 

 Stalactites, substances deposited in caves or the fissures of rocks from the droppings 



of water which contain lime in solution. 

 Sternum, the breast-bone. 



Stigma, in Botany, the extremity of the germ or seed-vessel of flowe:s. 

 Stimuli, substances which stimulate or excite. 

 Strata, beds, layers. 

 Subclavian, lying underneath the clavicle or collar bone ; as the subclavian artery 



the sub Flavian vein. 

 Substratum, foundation, groundwork. 

 Subtend. A line which passes across from one of the lines forming an angle, to the 



other, is said to subtend that angle. 



Sulphureted hydrogen, hydrogen combined with a portion of sulphur. 

 Suture, a mode of union which takes place in the bones of the head and face, in 



which the edge of one bone is let into that of another by means of correspond- 

 ing indentations in each, ths line of union appearing like a seam (sutura), 



whence the name. 

 Tendons, white, smooth, and strong cords by which muscles are generally fixed to 



the bones ; usually called cords or sinews. 

 Tendrils, the filaments by which creeping or climbing plants attach themselves to 



other objects for support, as those of the vine, ivy, &c. 



